While I was a postdoc in the laboratory of Anjana Rao, we produced knockin hnRNPLL ES cells. These cells were injected into blastocysts in the Mouse Cancer Genetics Program, and chimeric mice were generated and bred. Southern blot confirmed germline transmission. These mice are presently being bred to homozygosity and are being crossed to Cre-recombinase expressing mice for conditional expression in T cells and B cells. Within the B cell lineage, hnRNPLL is solely expressed in plasma cells, which do not express significant CD45. By knocking hnRNPLL into B cells, we expect to identify additional targets, and expect to see characteristics of plasma cells early in B cell development. In contrast, hnRNPLL is expressed in thymocytes, but is down-regulated before exit to the periphery. HnRNPLL is once again up-regulated in activated T cells. By knocking hnRNPLL into thymocytes, we expect to see altered lymphocyte selection in the thymus, possibly resulting in immunodeficiency or autoimmunity. Given the dramatic up-regulation of hnRNPLL in dividing T cells, we also expect to see altered proliferation kinetics as a result of inappropriate expression in naive T cells. A construct for conditional hnRNPLL knockout was developed when I was a postdoc in the laboratory of Anjana Rao. The construct was targeted into ES cells and chimeric mice were generated in conjunction with the transgenic facility of the Mouse Cancer Genetics Program. These mice are presently being bred and germline transmission will be assessed by Southern Blot. Germline mice will be crossed to Cre-expressing strains for conditional deletion of hnRNPLL in lymphocytes. The expected outcomes will the opposite of what was described above.